Best Root Cause Analysis Tools and Methods

You know that looking at symptoms of a problem is not enough to resolve it.

You need to strike at the core of a problem by finding its key and root causes. This is where the root cause analysis tools and techniques come to help businesses resolve the situation by finding the best possible solutions.

On this page:

  • What is the root cause analysis (RCA)? Definition.
  • Top 5 RCA tools and methods in use nowadays (The 5 Whys, Fishbone Diagram, Is/Is Not Analysis, FMEA, Affinity Diagram).

As the name suggests, root cause analysis is a way for identifying the key causes of an event. The goal is to be found and implemented the most effective solutions.

It’s commonly used when the things go wrong, but can also be used when the things go very well. RCA can be applied to almost any kind of problem that businesses face every day.

From manufacturing problems to incorrect customer shipments, RCA applications are endless and can result in significant improvements in the business processes.

There are a lot of tools and methods that may be used during a Root Cause Analysis. Some of them can be completed by one person, but in most cases, a team approach is the right one.

Let’s see the most popular root cause analysis tools in use today:

The 5 Whys

As you might guess, The 5 Why method means you asking the question “Why”. You have to ask “Why” as many times as needed until you pass all the symptoms of a problem and get to the root cause.

Commonly, the answer to the first “why” should suggest to another “why” and the answer to the second “why” will suggest to another and so on.

The Five Whys is a simple RCS tool and technique that help you to fast determine the root cause of a situation. It’s simple and very easy to apply.

The Five Whys is most useful when the problem involves human factors and interactions.

Although this method is called “5 Whys,” there are many situations where you will need to ask the question fewer or more times than five before you find the core reasons for the problem.

The 5 Whys RCA

This technique produces linear regression models and sets of casual relationships and uses the experience of the problem owner to identify the key cause and possible solutions.

Fishbone Diagram

Also known as Cause–and–Effect Diagram and Ishikawa Diagram, Fishbone is one of the most popular root cause analysis tools and methods out there.

It identifies many possible causes for a problem. This diagram-based technique that involves Brainstorming and a visual display of many potential causes for a given problem.

In a fishbone diagram, the causes are grouped into categories. These categories are brainstormed by the team. Typical categories include equipment, materials, processes or methods, measurements, environment, and people.

Fishbone Diagram - one of the best Root Cause Analysis Tools


This type of root cause analysis aims to understand the possible causes by asking questions such as “what happened,” “where,” “when,”“why,” “how,”. The questions are asked until a possible cause is identified and the consequences are found for each category.

This RCA tool is very useful when you’re trying to solve complicated and complex problems. More for Fishbone diagram you can find on the ACQ page.

Is/Is Not Analysis

Is/Is Not Analysis is a simple but very powerful tool for root cause analysis used to understand the problem and the scope of it. This analysis answers the questions what was and what was not made in order to produce the effect.

It is often used in combination with other quality management tools such as 5 Whys and Fishbone analysis.

The Is-Is Not analysis allows you to think about the problem and the boundaries of what it is or is not. Thus the tool helps you maintain your focus. It is crucial to define the boundary of the problem otherwise you may stray off the path and work on solving meaningless problems.

The analysis is followed by the ” What Is and Is Not” document that is a part of the characteristic of the problem.

Is-Is Not Analysis

The process goes by asking the team different types of questions such as: “Who is influenced by this problem?”, “What do we know about the problem?”, “Will we actually can do something?” and etc.

Asking the questions last until there is a clear definition of the problem and its scope.

This analysis is used when a problem is being identified to decide what is in scope and what is not important at this time.

Affinity Diagram

The Affinity Diagram, also known as a KJ diagram, is a part of Seven Management and Planning Tools, invented for organizing a lot of ideas and data.

As one of the root cause analysis tools, it is used to generate and organize information relevant to the issue in question. It is it is typically used directly after brainstorming to sort large numbers of ideas and possible causes of a problem into groups.

The Affinity Diagram allows you to represent the structure of big and complex factors which impact a problem or a situation. Also, it splits these factors into smaller groups (according to their similarity) and helps teams to identify the major causes.

Affinity Diagram 2

An affinity diagram should be used to encourage discussion about a problem, seeing the patterns and identifying possible solutions or improvements.

This analysis is used when a problem is large and complex and includes a lot of factors and causes.

Failure Mode and Effects Analysis (FMEA)

Failure Mode and Effects Analysis is a structured approach for evaluating a process to identify potential failures that may exist within the design of a product or a process.

Failure modes are the directions in which a process can fail. Effects are the ways that the failures can lead to bad outcomes. FMEA aims to define and limit these failure modes.

Failure Mode and Effects Analysis

FMEA is one of root cause analysis tools with a systematic approach, created with the help of a spreadsheet. It allows you to anticipate what might go wrong with a product or process. FMEA helps to define the possible causes of failures.

Used by many businesses, FMEA is one of the best ways of analyzing potential problems early in the development stage, making it easier for you to take quick action and soften the failure.


Root cause analysis tools and techniques aim to improve products and processes. They allow you to find out why your projects are not what were expected to be.

Each one of the above tools can be combined with one or more other RCA tools depending on the situation. Combining these tools is often necessary and very important.

Although the most root cause analysis methods and techniques have the expected results if they are properly applied, it is crucial to make sure the team knows how to use and apply them.

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